Various types of seat slide apparatuses for a vehicle have been disclosed in the past. For example, JPS58-19836U, hereinafter referred to as Reference 1, discloses a seat slide apparatus for a vehicle including a lower rail having flange portions and an upper rail embracing the flange portions. Incisions are made on an upper plate portion of the upper rail near each of the opposing ends, and cut out portions are formed on an inner edge of the flange portion of the lower rail at the opposing end portions. On assembling an apparatus having such structures, the lower rail is inserted to the upper rail first, then the portions where the incisions are made on the upper rail are bent in an inward direction to form cut-and-bent portions. The upper rail moves relative to the lower rail, however, an amount of the relative movement between the upper rail and the lower rail is limited to a predetermined amount by making a cut-and-bent portion come into contact and stop in an engaged state with a step portion of the lower rail, which is a portion the cut out portion provides.
In Reference 1, the cut-and-bent portions of the upper rail restrict the relative movement between the upper rail and the lower rail with only one side of the rails. In order to provide an adequate rigidity for the structure, a thickness of the upper rail, for example, may be increased.
FIGS. 9A and 9B illustrates a known seat slide apparatus for the vehicle including the lower rail 91 having a substantially U-shaped cross section provided with a pair of side wall portions 91a and the upper rail 92 attached inward of the lower rail 91 and configured to move relative to the lower rail 91. In this known seat slide apparatus for the vehicle, locking pins 93 are provided across the side wall portions 91a in a width direction with the opposing ends of each of the locking pins 93 being fastened to a corresponding side wall portion 91a such that blocks movements of end surfaces 92a of the upper rail 92. As a result, the amount the upper rail 92 moves relative to the lower rail 91 is limited to a predetermined amount by making the end surfaces 92a of the upper rail 92 come into contact and hold in engaged state with the corresponding locking pin 93. Each of the locking pins 93 restricts the relative movement of the upper rail 92 by holding the end surface 92a with both of the opposing sides in the width direction of the lower rail 91, so that an adequate rigidity for the structure may be provided.
With such a structure, however, a distance provided in the direction of the relative movement between the end surface 92a and the locking pin 93 defines the amount of the upper rail 92 moving relative to the lower rail 91 provided that the positions of the locking pins 93 are fixed to predetermined positions. In other words, the length of the upper rail 92 defines the amount of the upper rail 92 moving relative to the lower rail 91. While the length of the lower rail 91 being unchanged, when the length of the upper rail 92 changes, the amount of the relative movement between the lower rail 91 and the upper rail 92 automatically changes. As a result, flexibility for adjusting the amount of the relative movement between the lower rail 91 and the upper rail 92 significantly decreases.
A need thus exists for a seat slide apparatus for a vehicle, which is not susceptible to the drawback mentioned above.